1. Well-defined myotactic reflexes (retractor-extensor thrusts) can be elicited from the retractor and extensor musculature when these muscles contract against an external resistance. A de-afferentated limb cannot exert a retractor-extensor thrust.
2. A retractor-extensor thrust arising in a forelimb evokes an extensor response in the diagonal hindlimb and a protractor response in the contralateral forelimb. In order that these responses should display themselves with regularity it is necessary to de-afferentate the responding limb; in an intact limb they are often masked by the control exerted by the limb's own proprioceptive mechanism.
3. In an intact animal a retractor-extensor thrust in a forelimb evokes a ‘placing reaction’ from the ipsilateral hindlimb. This phenomenon is only partially displayed if the hindlimb is de-afferentated.
4. When an intact forelimb responds, by protraction, to passive stretch, the contralateral hindlimb flexes and the ipsilateral hindlimb extends if the latter limbs have been de-afferentated.
5. The individual proprioceptor limb responses integrate to form an adequate picture of the co-ordinated limb movements seen when an intact toad ceases to swim and begins to walk on land.
6. The role of proprioceptor activity in the maintenance of an ambulatory rhythm in a single limb is discussed.